Women who are obese at the start of their pregnancy may be passing on insufficient levels of vitamin D to their babies, according to a new Northwestern Medicine® study. The study found that babies born to lean mothers had a third higher amount of vitamin D compared to babies born to obese moms. Vitamin D is fat-soluble, and previous studies have found that people who are obese tend to have lower levels of the vitamin in their blood. In this study, both obese and lean mothers had very similar levels of vitamin D at the end of their pregnancies, yet obese women transferred less vitamin D to their offspring compared to lean women.